In the automobile industry or machinery industry, etc., there has been increased demand for sensors capable of precisely detecting acceleration or angular velocity of a moving object. In regard to an acceleration, sensors of various types have been conventionally proposed, and smallsized sensors capable of two-dimensionally or three-dimensionally detecting an applied acceleration have been put into practical use. For example, in the International Publication No. W088/08522 based on the Patent Cooperation Treaty (U.S. Pat. No. 4,967,605/U.S. Pat. No. 5,182,515), an acceleration sensor utilizing changes of resistance values of piezo resistance elements formed on a semiconductor substrate is disclosed. Moreover, in the International Publication No. WO92/17759 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,492,020), there is disclosed an acceleration sensor in which electrostatic capacitance elements or piezoelectric elements are used to detect an applied acceleration in every respective coordinate axis direction. In the International Publication No. W093/02342 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,365,799), there is disclosed a multi-axial acceleration sensor using piezoelectric elements of different type.
On the other hand, there are a relatively few publications in connection with the angular velocity sensor. Particularly, publications in regard to angular velocity sensors capable of simultaneously detecting angular velocity about multi-axes can be hardly seen. Ordinarily, angular velocity sensors are utilized for the purpose of detecting an angular velocity of a power shaft, etc. of vehicle, and only have a function to detect an angular velocity about a specific one axis. In such a case that a rotational speed of the power shaft as described above is measured, it is sufficient to use a one-dimensional angular velocity sensor. However, as a sensor for detecting angular velocity with respect to an object which carries out free movement within a three-dimensional space, multi-axial velocity sensors capable of simultaneously detecting angular velocity components about two-axes or three-axes are expected.
In order to meet with such demand, the inventor of this application has proposed novel multi-axial angular velocity sensors in the International Publication No. WO94/23272 based on the Patent Cooperation Treaty (U.S. patent application Ser. No. 08/366026) and the Japanese Patent Application No. 7-56690/1995 specification (U.S. patent application Ser. No. 08/601794). Such novel angular velocity sensors utilize the principle that when an angular velocity is applied about the second coordinate axis to the object moving in the first coordinate axial direction in the XYZ three-dimensional rectangular coordinate system, Coriolis force is produced in the third coordinate axial direction, and the sensors detect Coriolis force applied to the object so as to indirectly detect an angular velocity. For detecting Coriolis force, the technologies which have been fostered in the conventional acceleration sensors are applied. That is, a piezo resistance element, a capacitance element and a piezoelectric element, etc. are utilized.